Alloy steel



Patented Oct. 14, 1930 UNITED STATES PATENT OFFICE JOHN A. NELSOIW OFROCKFORD, ILLINOIS, ASSIGNOR 'I'O BARBER-OOLMAN COMPANY, OF ROCKFORD,ILLINOIS, A CORPORATION OF ILLINOIS ALLOY STEEL Ho Drawing.

employed requires a high temperature and the combined effect of thecharacter of the steel and of the heat treatment has been such as tocause a deformation of the tool from the-form and dimensions in'which itwas initially prepared. In the heat treatment the tool may warp or twistand is usually so distorted that it' requires a truing process to makeit an accurately formed tool "suitable for machine work. This is usuallydone by a grinding process. To prepare the tool for the heat treatmentthere is provided for the subsequent grinding operation a sufficientexcess of material, or an allowance in dimensions is made in the initialformation of the to'ol for the customary deformation.

The object of the present invention is to provide'a composition of steelwhich'is less subject to distortion on heat treatment and which has alowered upper temperature limit for the heat treatment wherein thedistortion is likely to take place. By the use of alloy steels embodyingthe invention, the

tool may be accurately formed prior to the heat treatment so that notruing or finishing operation is requiredl Ofcourse it is to beunderstood that this condition represents the ideal attainment of theobject of the invention and may be limited to a definite composition andto a correspondingly proper heat treatment. But it is tobefurtherunderstood that there may be variations in the compo sition withincertain ranges, and variations in the. heat treatment which will yieldthe samefcharacter of results and in which some slight distortion of thetool is permitted, or

in which a slight amount of-refinishing may be necessary depending uponthe degree of accuracy required for the tool. It is, therefore, to beunderstood that the invention is not limited to the'ideal condition butcontem-- plates thosealloys which exhibit an'improvethe range ofcomposition when cobalt is em- Application filed September 14, 1925.Serial No. 56,133.

ment over alloys of the prior art in the direction of the idealcondition.

The invention comprises a fundamental or base alloy steel having thefollowing range of composition for the chief ingredients other thaniron:

Carbon 1.00% to 1.75% Chromium 4.00 10.00 Tungsten 6.00 10.00

However, in order to improve the above base alloy for use in makingcutting tools, a quantity of vanadium is added to improve the cuttingqualities, but without affecting the desirable qualities of the basealloy. Therefore, for cutting tools the alloy is preferably of thefollowing composition:

Carbon- 1.00% to 1.75% Chromium 1.00 10.00 Tungsten 6.00 10.00 Vanadium0.50 2.00

Alloys according to the above range are very suitable for thread mills,taps and other tools which are not operated at high speeds. 75. Highspeed tools, of course, are subject to greater wear in use per unit worktime, and require, therefore, a composition giving long life. While thebase alloy above described might be used for high speed tools, it ispreferable that it be used for the slower type of tools. However, when asecond metal of the iron group is added, the steel becomes better suitedfor high speed work. Cobalt is the second metal which is preferablyadded since this increases the life of the cutting edge and does notappear in any way, to alter the hardening temperature or thenon-shrinkable qualities of the alloy. The following shows ployed:

Carbon 1.00% to 1.75% Chromium {1.00 10.00 Tungsten 6.00 10.00 Vanadium0.50 2.00 Cobalt 3.00 1500 Within the above range of cobalt, 7% to 8% isthe preferable upper limit so far as economic cost is considered, for anincreased 100 percentage over that amount does not improve the qualityin proportion to the cost. I

In addition to cobalt, as a metal of the iron group, nickel may be addedas this may increase the toughness of the tool. It also lowers thehardening temperature. The nickel preferably may vary from 0.7 5% to2.00%. Carbon as an element of the alloy is also related to theheat-treating process. In general carbon lowers the hardeningtemperature, but below 1% carbon a raising of the hardening temperaturecommences. For example, a 1% carbon alloy can be satisfactorily treatedat 1875 F. to 1900 F., quenched inoil, and drawn to 1000 F. A 09% carbonalloy must be hardened at 2000 F. to give satisfactory results and aconsiderable increase in distortion takes place over that which occursin the 1% carboir'alloy. For an alloy of this invention it is preferredto use a carbon content varyingfrom 1.05% to'1.15%, because as thecarbon content increases the brittlenessalso increases. It is to beunderstood, however, that this preference does not exclude higherpercentages of carbon.

Chromium is believed to increase the solubility of the carbides uponhardening, and in conjunction with the carbon lowers the hardeningtemperature and also increases the hardness. It has been foundthat there1s little-change in the cutting properties by Varying the chromiumcontent from 52]- to 8%. However, whenchromium rises above 10% themovement of metal upon hardening v is greatly increased and there is inaddition a loss of hardness on tempering. It is believed that 10% is aproper upper limit for chromium. When quenched froml875- F. to 1900 F.and then drawn to 1000 F., the proper hardness .is not obtained whenthere is less than 4% chromium. 4% then is preferred as a lower limitforthe chromium range in this invention.

In general tungsten increases the hardness and raisesthe temperature atwhich tempering, can be effected after hardening,'without destroying thehardness. Tungstenproduces little change when varied from 6 to 9%. Above10% it is found that thedistortion is so great as to render the allouseless for the desired advantages. There ore, 10% is belieived to be aproper upper limit for tungsten.

Vanadium does not materially change the deslred physical properties'ofthe alloy, but it has been found to increase the. cuttingetficiencyof tools employing it when alloyed This is, of

with the other components. course, of great importance when the alloy isused for tools.

In steels ascommercially prepared, there is of course, a tolerance ofindustrial impuri ties, such as silicon, manganese, phos horns,

and sulphur, the presence of which a cot the properties of the alloyeither beneficialll or entering into the composition.

detrimentally depending upon the particular property to be consideredand the amount of as follows:

Carbon; 1.05% to 1.15% Chromi-uni 7.50 8.50 Tungsten 8.00 9.00 Vanadium1.00 1.50 Cobalt 7.00 9.00 Silicon 0.20 0.30 Manganese 0.20 0.30Phosphorus below 0.030 Sulphur below 0.030

In all of the above tables it is understood that the remainder of thepercentage is iron.'

may also be cooled in air from a heat treatment between 1700? F. and12050" F. and stillhe tile-hard. Other conditions of heat treatmentmayalso be found satisfactory for alloys within the range ofcompositionhereinafter claimed. 4 I

The invention consists primarily of the said alloy of iron, carbon,chromium and tungsten which is adapted to resist distortion and to benon-shrinlmble during heat treatment like other steels. It issusceptible to improvements in its cutting properties. by the additionof vanadium in the amount stated, without affecting its desirabledistortion-resisting properties and furthermore, it is subject toadditional improvements in high speed cutting properties by the additionof cobalt, and this likewise, without influencing its speciallydesirable properties, when the cobalt is limited as stated.

In the appended claims, the invention is defined so as to include notonly the base alloy per se, but such combinations of the'basealloy withother metals as preserve the desired qualities of theiron-carbon-tungsten-chromium-alloy, such combinations having, inaddition, various improved characteristics in other directions.

I claim as my invention:

1. A steel alloy containing carbon 14.7 5%,

' chromium 41-10%, tungsten 63-10%, vanadium 0.5 2%, as the chiefingredients, and the princlpal part of the remainder being iron.

2. A steel alloy containing carbon 1-1.75%,

chromium 440%, tungsten 610%, vanadium 0.52%, and cobalt 345%, as thechief ingredients, and the principal part of the remainder iron.

3. A steel alloy containing carbon 1.05-1.15%, chromium 7 .58.5%,tungsten 89%, as the chief ingredients, and the principal part of theremainder iron.

AA steel alloy containing carbon 1.05-l.15%, chromium 7.58.5%, tungsten89%, vanadium 11.5%, cobalt 7 9%., as the chief ingredients, and theprincipal part of the remainder iron.

5. A steel alloy containing carbon 1.051.15%,; chromium 7.58.5%,tungsten 8.9%, as the chief ingredients, and containing silicon 0.2-O.3%; manganese Oil-0.3% phosphorus below 0.03%, sulphur below 0.03%,and the remainder iron. 6. A steel alloy containing carbon l.051.15%,chromium 58%, tungsten 69%, vanadium- 0.52%, cobalt 7 -8%, and theprincipal part of the remainder iron. 71 A substantially undistortedheat-treated metal-cutting tool made of an alloy according to claim 3,said tool being formed accurately prior to heat treatment.

ing to claim 6, said tool being formed accurately prior to hardening.

In testimony whereof, I have hereunto affixed my signature.

JOHN A. NELSON.

8. A substantially undistorted heat-treated metal-cutting tool made ofan alloyaccord--

